Fuel injection system for internal combustion engines



g- 26,1969 RBABITZKA ETAL 3,463,129

FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES Filed Oct. 13, 1967 2 Sheets-Sheet 1 FIG] 25 o 22 l. t

14 g 19 18 J A L '17 L M FIG 2 7 INVENTORS 23 Rgdolf BABITZKA Gunther BAUMANN Hermann HOE LLE Hermann SCHOLL their ATTORNEY Aug. 26,1969 R. BABITZKA ET AL 3,463,129

NUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES Filed Oct. 13, 1967 2 Sheets-Sheet 2 I t I I 45 l 35 a *1 i 1| t t t t'- 1 3 4 Y INVENTORS Rudolf BABITZKA Gunther BAUMANN Hermann HOELLE germcmn SCHOLL their ATTORNEY United States Patent Int. Cl. F02]: 3/60; F02rn 39/00 U.S. Cl. 123--32 7 Claims ABSTRACT OF THE DISCLOSURE The electronic control unit which effects opening and closing of electromagnetic fuel injection valves in a fuel injection system for internal combustion engines receives impulses from a signal generator which is responsive to pressure changes in the intake manifold of the engine. The magnitude of impulses determines the length of intervals during which the fuel injection valves remain open. The signal generator comprises an output portion which is electrically connected with the control unit and an input portion having a chamber which is in permanent communication with the intake manifold through one or more flow restricting openings serving to prevent the input portion from influencing the output portion in response to minor pressure fluctuations in the intake manifold resulting from repeated opening and closing of inlet valves for individual cylinders. A relief valve is provided in parallel with the flow restricting opening or openings to open automatically when the pressure differential between the intake manifold and the chamber of the input portion exceeds a predetermined value.

BACKGROUND OF THE INVENTION The present invention relates to fuel injection systems for internal combustion engines, and more particularly to improvements in the costruction of fuel injection systems whose operation depends on pressure changes in the intake manifold of the engine.

A serious drawback of presently known fuel injection systems is that they react to all pressure changes in the intake manifold, i.e., also to those changes which are not due to adjustments of the throttle valve which is controlled by the gas pedal. Such pressure changes or fluctuations develop periodically due to repeated opening and closing of intake valves. At certain rotational speeds of the engine, periodically recurring pressure fluctuations in the intake manifold can cause undesirable oscillations of the signal generator which sends impulses to the control unit for the fuel injection valves.

SUMMARY OF THE INVENTION It is an object of our invention to provide a fuel injection system which is constructed and assembled in such a way that it cannot be influenced by minor pressure fluctuations in the suction manifold of an internal combustion engine.

Another object of the invention is to provide the fuel injection system with a signal generator which can discriminate between those pressure changes in the intake manifold which should affect the operation of fuel injection valves and such fluctuations which should not affect the fuel injection system.

A further object of the invention is to provide a signal generator which is not responsive to such pressure changes in the intake manifold which develop solely as a result of repeated opening and closing of intake valves in the cylinders of an internal combustion engine.

3,463,129 Patented Aug. 26, 1969 Our invention is embodied in a fuel injection system comprising normally closed electromagnetic fuel injection valves installed in the branches of an intake manifold which is connected with the cylinders of an internal combustion engine so that the valves may inject fuel when moved to open positions by the output stage of an electronic control unit which opens the valves at intervals determined by the r.p.m. of the crankshaft of the engine and for periods whose duration depends on the pressure in the intake manifold, and signal generating means for transmitting to the control unit signals whose magnitude indicates the pressure in the intake manifold. The signal generating means comprises an output portion electrically connected with the control unit and an input portion having a chamber which communicates with the intake manifold through flow restricting means which delays the equalization of pressures in the manifold and the chamber so as to eliminate the influence of minor fluctuations of pressure in the intake manifold.

In accordance with another advantageous feature of our invention, the signal generating means preferably comprises at least one relief valve which opens when the pressure differential between the intake manifold and the chamber of the input portion exceeds a predetermined value. Such relief valve is preferably installed in parallel with the flow restricting means and can open when the pressure in the intake manifold exceeds the pressure in the chamber by a predetermined value or vice versa.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved fuel injection system itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic side elevational view of an internal combustion engine which embodies the improved fuel injection system;

FIG. 2 is an enlarged axial sectional view of the signal generating means in inverted position;

FIG. 3 is an enlarged fragmentary axial sectional view of a detail of the signal generating means;

FIG. 4 is a diagram showing the relationship between the pressures in the signal generating means and intake manifold when the connection between these parts merely includes a flow restricting opening; and

FIG. 5 is a similar diagram showing the relationship between the pressures when the connection between the intake manifold and signal generating means includes a flow restricting opening and a relief valve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a four-cylinder internal combustion engine 10 whose spark plugs 11 are connected with and receive current from a suitable ignition system, not shown. An intake manifold 12 has four branches each of which is connected with one of the four cylinders in the engine 10. The intake valves are not shown in the drawings. These intake valves are immediately adjacent to four electromagnetic fuel injection valves 13 which form part of the novel fuel injection system and each of which is installed in one of the four branches of the intake manifold 12. The magnetic windings of the injection valves 13 have pairs of poles one of which is grounded and the other of which is connected to one of four resistors 14 and through the respective resistor with'the collector of one of two transistors 15, 16 together constituting the output stage 17 of an electronic control unit 18 of known design. Such control units are shown, e.g., in US. Patents 3,005,447 and 3,203,410. The control unit 18 is coupled with the output of a timer circuit 19 which produces signals in synchronism with the r.p.m. of the diagrammatically indicated camshaft 10a of the engine 10. The control unit 18 further receives signals from a signal generator 22 which is connected with the intake manifold 12 by a conduit 23 and whose output portion produces signals or impulses of a magnitude or intensity which is indicative of the pressure in the intake manifold. The signals transmitted by the output portion of the signal generating device 22 are used to influence the length of intervals during which the output stage 17 of the control unit 18 maintains the fuel injection valves 13 in open position. The output portion of the signal generator 22 may include a resistor whose resistance varies as a function of pressure changes in the intake manifold 12, a capacitor whose capacitance changes in the same way, or an inductance whose inductivity also changes in dependency on pressure changes in the manifold 12. At this time, we prefer to employ an output portion which comprises a variable inductance. Our present invention deals primarily with the manner in which the input portion of the signal generator 22 is connected with and can influence the output portion in dependency on changes in pressure which momentarily prevails in the intake manifold 12.

The pipes or hoses 24 shown in FIG. 1 consittute con nections between the normally closed fuel injection valves 13 and a source of fuel which includes a distributor tank 25 containing a supply of fuel under constant pressure, a fuel pump 26 which feeds fuel to the distributor tank 25, and a fuel storage tank 27 which is connected with the intake of the pump 26. The amounts of fuel which are injected into the cylinders of the engine 10 depend on the length of intervals during which the valves 13 are opened by the control unit 18.

The inlet of the intake manifold 12 accommodates a throttle valve 29 whose position is adjustable by a gas pedal 28. The valve 29 admits into the manifold 12 air which passes through an air filter 30. If the valve 29' is closed, the pressure in intake manifold 12 drops. When the valve 29 is opened by the pedal 28, the pressure in the manifold 12 equals atmospheric pressure.

FIG. 12 illustrates one embodiment of the signal generator 22. This signal generator includes a housing having two cupped sections or halves 34, 35 which are sealingly connected to each other and accommodate an electrical output portion (in the section 34) which transmits signals to the control unit 18 and an input portion which comprises a chamber including the section 35, the connecting conduit 23, a partition 35a between the sections 34, 35, and two deformable diaphragm assemblies 36, 37 in the interior of the section 35. It is to be noted that the signal generator 22 is shown in FIG. 2 in inverted position, i.e., with the conduit 23 extending downwardly. Each of the diaphragm assemblies 36, 37 comprises an evacuated box of sheet metal which contracts when the pressure in the chamber rises but expands in automatic response to a drop in chamber pressure. The assemblies 36, 37 resemble customary metallic boxes which are often employed in aneroid barometers. The conductors which connect the output portion with the circuit of the control unit 18 are not shown in the drawings. This output portion comprises an inductance having a winding 38 accommodated in a ferrous part 39 of substantially U-shaped crss-section. A cylindrical iron core 42 is reciprocable in the central passage of the winding 38 under or against the bias of a helical spring 41. This core 42 is connected with and is shiftable axially in response to deformation of diaphragm assemblies 36, 37.

The operation of the signal generator 22 is as follows:

If the pressure in the chamber of the input portion is low, the diaphragm assemblies 36, 37 expand and the core 42 is shifted upwardly against the opposition of the spring 41, i.e., the core 42 is moved out of the passage of the winding 38. This reduces the inductivity of the inductance and the latter sends an appropriate signal to the control unit 18. If the pressure in the chamber of the input portion rises, the diaphragm assemblies 36, 37 allow the core 42 to move downwardly under the bias of the spring 41 and the inductivity of the inductance increases.

In accordance with one feature of our invention, the input portion of the signal generator 22 comprises flow restricting means which delays the equalization of pressures between the aforementioned chamber in the input portion and the interior of the intake manifold 12. This flow restricting means is constituted by an opening or bore 46 (shown in FIG. 3) which establishes permanent communication between the interior of the section and the intake manifold 12.

According to another advantageous feature of the present invention, the flow restricting opening 46 is provided in parallel with a pressure relief valve 43 which is normally closed and operates between the conduit 23 and the section 35. The relief valve 43 comprises a disk-shaped valve member 44 which is installed in the section 35 and normally bears against an annular seat 45 of the section 35 as shown in FIGS. 2 and 3. A leaf spring 47 biases the valve member 44 against the seat 45. The flow restricting opening 46 is provided in the valve member 44 but it is clear that this opening could be provided in the seat 45 or in another part of the section 35 or conduit 23, as long as it can establish communication between the intake manifold 12 and the chamber of the input portion of the signal generator 22. Since the pressures which are controlled by the relief valve 43 are rather low, the wear on the valve member 44, seat 45 and spring 47 is negligible.

The leaf spring 47 which is mounted in and is attached to the section 35 preferably biases the valve member 44 to closing position with a force which suffices to normally prevent opening of the relief valve 43 but allows such opening when the pressure differential between the intake manifold 12 and the chamber defined in part by the section 35 approximates or exceeds 0.05 kp./cm. i.e., when the pressure in the intake manifold 12 exceeds the pressure in the section 35 by such relatively small value. This insures that the relief valve 43 does not open in response to normal fluctuations in pressure which prevails in the intake manifold 12 but will open as soon as the pressure in intake manifold rises above the pressure in the chamber of the input portion beyond a predetermined extent. Normal fluctuations in pressure which prevails in the intake manifold 12 are communicated to the interior of the section 35 through the flow restricting opening 46, but such fluctuations are damped by this opening and cannot unduly influence the magnitude of signals which are transmitted to the control unit 18.

FIGS. 4 and 5 illustrate the changes of pressure (12 in the intake manifold 12 and the corresponding changes of pressure (17 in the chamber of the input portion of the signal generator 22. FIG. 4 shows how the pressure changes as a function of changes in pressure 12 when the relief valve 43 is omitted so that the intake manifold 12 communicates with the interior of the section 35 only through a flow restricting opening corresponding to the opening 46. FIG. 5 shows the relationship between the pressures p and 11;, when the signal generator 22 includes a relief valve 43 and a flow restricting opening 46.

When the driver of the vehicle accelerates the engine by depressing the pedal 28, pressure 12 in the intake manifold 12 rises rapidly but the rise of pressure p lags in a manner as shown in FIG. 4 if the relief Valve 43 is omitted or is permanently closed. This is due to the fact that the opening 46 permits the flow of limited amounts of fluid per unit of time. If the acceleration of the engine begins at the time 1 it requires a relatively long interval (i -r before the difference between the pressures p and J (FIG. 4) is reduced to a relatively small value Ap.

However, if the signal generator 22 comprises a flow restricting opening 46 and a relief valve 43, it requires a much shorter interval of time (t t in FIG. 5) before the difference between the pressures p and 12 decreases to Ap. Thereupon, the difference Ap remains substantially unchanged during the remainder of acceleration. If the pressure differential drops below Ap (at the time indicated by the line L; in FIG. 5), the relief valve 43 closes automatically under the action of its spring 47 and the equalization of pressures is thereupon effected solely through the opening 46 in the same way as described in connection with FIG. 4.

A comparison of FIGS. 4 and 5 shows that the ratio of intervals t t to t t is about six-to-one. In other words, the relief valve 43 is six times more effective to insure that the difference between the pressures p and p cannot exceed a permissible value Ap. The opening 46 and relief valve 43 improve the operation of the fuel injection system during acceleration of the engine by resorting to a very simple arrangement of parts which occupy little room and undergo negligible wear. By providing the signal generator 22 with a second relief valve (not shown) which opens when the pressure in the intake manifold 12 is less than the pressure in the chamber of the input portion, equally satisfactory results can be achieved during deceleration when the driver causes the the pedal 28 to close the valve 29 in the intake manifold 12.

The main purpose of the relief valve 43 is to insure rapid equalization of pressures p and 12, on sudden opening of the throttle valve 29. Were the valve 43 permanently closed or absent, the opening 46 would prevent rapid rise of pressure 12;, and the electronic control unit 18 would react with a certain delay following opening of the valve 29. In normal operation of the engine 10, the relief valve 43 remains closed and the opening 46 prevents fluctuations of pressure 2 which develop on repeated opening and closing of intake valves from influencing the control unit 18.

It is further clear that the relief valve 43 can be replaced with a pilot relief valve which responds to pressure differentials in either direction to open automatically when the pressure p exceeds the pressure p by the value Ap or vice versa. The exact design and/ or number of relief valves will depend on the type of the internal combustion engine and the nature of the fuel injection system. It was found that a pressure differential Ap in the range of 0.05 kp./cm. is very satisfactory to achieve a good transition during acceleration of the engine and to insure that normal fluctuations of pressure 2 cannot cause opening of the relief valve 43.

The relief valve can be of simple design because it is not subjected to appreciable stresses. If the valve member 44 requires replacement, the opening 46 is replaced therewith provided, of course, that this opening is machined into or formed in the valve member.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of our contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

We claim:

1. In an internal combustion engine having cylinder means, intake manifold means connected with said cylinder means, means for regulating the pressure in said manifold means, a source of fuel and connecting means between said source and said manifold means, a fuel injection system comprising normally closed fuel injection valve means provided in said connecting means; control means for opening said fuel injection valve means for periods Whose length varies as a function of pressure changes in said manifold means; signal generating means for transmitting to said control means signals whose magnitude indicates the pressure in said manifold means, said signal generating means comprising a housing defining a chamber, pressure responsive means in said chamber, stationary means, and movable means mechanically connected to said pressure responsive means to be moved thereby in response to changes of pressure in said chamber and cooperating with said stationary means to produce an electrical signal whose magnitude corresponds to the movement of said movable means relative to said stationary means, one of said last mentioned two means being electrically connected to said control means; a connection between said chamber and said manifold means; flow restricting means in said connection to eliminate the influence of minor pressure variations in said manifold means on the pressure responsive means; and a bypass in parallel with said flow restricting means and including normally closed relief valve means constructed to open when the pressure in said manifold exceeds the pressure in said chamber by a predetermined value to quickly reduce the pressure difference between said chamber means and said manifold means when said pressure in the latter quickly changes, for instance during desired acceleration of the engine, to a considerable extent.

2. A fuel injection system as defined in claim 1, wherein said pressure responsive means comprises at least one diaphragm assembly deformable in response to pressure changes in said chamber, wherein said movable means comprises an iron core connected to said diaphragm assembly, and said stationary means comprises an inductance coil surrounding said core and electrically connected to said control means.

3. A fuel injection system as defined in claim 1, wherein said pressure differential is in the range of 0.05 kp./cm.

4. A fuel injection system as defined in claim 1, wherein said flow restricting means forms part of said relief valve means.

5. A fuel injection system as defined in claim 1, wherein said relief valve means comprises a seat, a valve member in said chamber and resilient means for biasing said valve member against said seat.

6. A fuel injection system defined in claim 5, wherein said flow restricting means comprises an opening provided in said valve member to establish permanent communication between said manifold means and said chamber.

7. A fuel injection system as defined in claim 1, Wherein said flow restricting means is dimensioned to prevent pressure changes in said chamber in response to such pressure fluctuations in said intake manifold which develop as a result of repeated opening and closing of intake valves in said cylinders.

References Cited UNITED STATES PATENTS 3,005,447 10/1961 Baumann et a1. 123-119 3,395,682 8/1968 Jackson 123--140 LAURENCE M. GOODRIDGE, Primary Examiner US. Cl. X.R. 

